Modulator

Abstract

In a modulator for converting two digital signals of I channel and Q channel in base band into analog signals and for converting a component of the signals whose phase is the same as a carrier and another component of the signals whose phase is orthogonal to the carrier so as to produce an orthogonally modulated wave, the two digital signals are connected to one signal train by time-sharing and multiplexing them and the converted analog signals are separated to two analog signals for the I channel and the Q channel and thereby a digital modulator can be structured by using only one digital/analog converter resulting in reducing the adjustment points and the production cost.

What is claimed is: 
     
       1. In a modulator for converting two digital signals for an I channel and a Q channel in the base band into analog signals and for modulating a component of the signals whose phase is the same as a carrier and another component of the signals whose phase is orthogonal to the carrier, comprising: signal connection means for connecting the two signals of said I channel and said Q channel to one signal train by time-sharing and multiplexing them;   a digital/analog converter for converting a signal connected by said signal connection means into a analog signal; and   signal separation means for separating an output analog signal converted by said digital/analog converter to two analog signals of said I channel and said Q channel.   
     
     
       2. The modulator according to claim 1 wherein a sampling points in the base band of said digital signals are offset between a time axis of said I channel and that of said Q channel. 
     
     
       3. The modulator according to claim 1 wherein said signal connection means causes said adjacent signal trains to be grounded for a particular time period when connecting the two signals to one signal train by time-sharing and multiplexing them. 
     
     
       4. The modulator according to claim 1 wherein a digital signal processing section is provided at least for mapping and filtering signals, said signal connection means being accommodated in said digital signal process section. 
     
     
       5. The modulator according to claim 1 wherein a digital signal processing section is provided at least for mapping and filtering signals, said digital signal processing section and at least one of said signal connection means, said digital/analog converter, and said signal separation means being accommodated in the same LSI.